This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-361515, filed Nov. 28, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention generally relates to an electronic part unit and circuit board apparatus to be incorporated in an electronic appliance, and more particularly to an electronic part unit and circuit board apparatus to be incorporated in a wireless communication terminal such as a portable telephone.
2. Description of the Related Art
An electronic part unit shown in FIG. 11 is conventionally known, which comprises an electronic part body 1 of a structure called a BGA (Ball Grid Array). The electronic part body 1 includes a carrier substrate 1B and a semiconductor chip 1A which is bonded to the carrier substrate 1B by a die bonding paste 1C. The semiconductor chip 1A on the carrier substrate 1B is encapsulated with a resin material 1G in a state where electrodes 1J on the carrier substrate 1B are connected to electrodes 1K on the semiconductor chip 1A by bonding wires 1E. The carrier substrate 1B has electrodes 1L formed on a rear surface thereof opposite to the semiconductor chip 1A and connected via through-holes 1D to the electrodes 1K, and a solder resist 1H surrounding the electrodes 1L so that solder balls 1F can be selectively attached to the electrodes 1L.
The electronic part body 1 described above is mounted, for example, on a printed circuit board 2 as shown in FIG. 12. To be more specific, the solder balls 1F are used for electrically connecting the electrodes 1L on the carrier substrate 1B to lead electrodes 2A on the printed circuit board 2. The printed circuit board 2 and the carrier substrate 1B are bonded to each other by an adhesive 3 made of an epoxy resin or the like filled in a space therebetween.
However, in the circuit board apparatus formed of the electronic part body 1 and the printed circuit board 2 integrated as described above, there is a possibility that the solder-contacts will be broken when the electronic part body 1 and the printed circuit board 2 are peeled off from each other due to a mechanical stress concentrated in the boundary therebetween, if the bonding area of the adhesive 3 is not sufficient. Further, the adhesive 3 tends to leak into the area surrounding the electronic part body 1 during the process of applying the adhesive 3 to the space between the electronic part body 1 and the printed circuit board 2, and to be undesirably attached to other electronic parts which should not be stained by the adhesive 3. Thus, it becomes necessary for the electronic part body 1 to be appropriately distanced from the other electronic parts. As a result, increase in the electronic part density of the printed circuit board is restricted.
The particular situation is not limited to the electronic part unit using the electronic part body 1 of the BGA structure. Similar difficulties also arise in electronic part units using various electronic parts, for example, of a structure called a QON (Quad Outline Non-lead).
An object of the present invention, which has been achieved in view of the situation described above, is to provide an electronic part unit and circuit board apparatus of a high reliability in which the mounting strength of an electronic part body is improved.
According to a first aspect of the present invention, there is provided an electronic part unit to be mounted on a printed circuit board, which unit comprises: an electronic part body which has a semiconductor chip and a plurality of external connection electrodes electrically connected to the semiconductor chip and in which the semiconductor chip is encapsulated such that the external connection electrodes remain exposed in a bottom surface of the electronic part body serving as a mounting surface opposed to the printed circuit board; and a cover member covering the electronic part body except for the mounting surface; wherein the cover member has a shape defining a space which receives an adhesive around a side surface of the electronic part body to bond the electronic part body and the cover member to the printed circuit board.
According to a second aspect of the present invention, there is provided a circuit board apparatus which comprises a printed circuit board; an electronic part body which has a semiconductor chip and a plurality of external connection electrodes electrically connected to the semiconductor chip and which is mounted on the printed circuit board, and in which the semiconductor chip is encapsulated such that the external connection electrodes remain exposed in a bottom surface of the electronic part body serving as a mounting surface opposed to the printed circuit board; a cover member covering the electronic part body except for the mounting surface; and an adhesive received in a space which is defined around a side surface of the electronic part body by the shape of the cover member to bond the electronic part body and the cover member to the printed circuit board.
With the electronic part unit and the circuit board apparatus, the shape of the cover member defines a space which receives an adhesive around the side surface of the electronic part body to bond the electronic part body and the cover member to the printed circuit board. Therefore, sufficient bonding strength can be obtained by improvement of the bonding area. Further, since the cover member can be used for completely sealing the adhesive on at least a side where another electronic part neighbors to prevent leakage of the adhesive, the electronic-part density of the printed circuit board can be improved.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.